2,2-Bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl] propane is recognized to be an effective flame retardant for numerous polymers including polycarbonates, polyurethanes, polyesters, copolyesters and the like. The compound can be blended with the polymer or employed as a coreactant and incorporated into the polymer structure.
One of the major drawbacks to the use of 2,2-bis[3,5 -dibromo-4-(2-hydroxyethoxy)phenyl] propane is the difficulty in obtaining the product in crystalline form. Conventional recovery processes produce the amorphous (non-crystalline) form of the product. While it is possible to flake or powder the amorphous material, upon storage at temperatures above about 30.degree. C the product "slumps" to form a solid mass. For most uses this requires that the product be reground or otherwise processed to put the 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl] propane in a form suitable for handling. The crystalline form on the other hand, does not slump and once flaked or powdered will remain indefinitely in the free-flowing condition as long as the temperature does not exceed the melt point of the material (115.degree.-120.degree. C).
In the past there has been no completely acceptable means to rapidly crystallize 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl] propane, especially when large quantities of material are involved. While it is possible to achieve crystallization by aging the material in small containers (up to about 50 pounds) for a week or more at 50.degree. to 75.degree. C, this technique is commercially unacceptable because of heat, space and time requirements. It would be highly advantageous and useful if a process were available to rapidly and economically crystallize 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl] propane. It would be even more desirable if such a process was adaptable to continuous or semi-continuous operation.